With fast development of wireless communication, it has become a core problem for next generation wireless communication systems to increase data transmission speeds without degrading the quality of service (QoS). Since Telatar found that multiple-input multiple-output (MIMO) systems are capable of linearly increasing channel capacity in 1995, research fever on wireless MIMO communication systems has been activated, and the MIMO technology has become a key technology in the next generation wireless communication systems. In addition, space-time codes are one of the main transmission technologies for long-term evolution (LTE) of the third-generation (3G) communication.
The MIMO communication system is divided into a coherent communication system and a non-coherent communication system based on requirement for channel estimation during demodulation. The non-coherent space-time code is divided into a differential space-time code and a unitary space-time code, and this invention is aimed at the unitary space-time code since there is very little research achievement for non-coherent unitary space-time demodulation methods. At present, experimental simulation platforms for designing the non-coherent space-time code mainly use a maximum likelihood algorithm as a demodulation algorithm. Maximum likelihood demodulation comprises calculating likelihood probabilities of all constellation points, and selecting a constellation point with the greatest likelihood probability as an output signal of a demodulator. However, a problem with the demodulation method traversing all the constellation points is that, calculation workload and complexity linearly increase as a constellation becomes larger.